Some people struggle with social boundaries / think relationships are deeper than they are / literally don't care about other people's preferences.
I had a person like this in my life, who actually moved a few doors down from me for a while (agh). She constantly asked for all kinds of favours and it was totally exhausting having to keep fielding her off. She'd also do it in such a way that she'd purposefully corner me (i.e. if she knew I was home for the night or had no plans, thus it was hard for me to come up with an excuse).
The only way to stop someone like this is to say no to literally every request. Better yet, if it's by text, ignore altogether and don't respond.
Otherwise, to say, "I don't like that you keep asking me for favours. It makes me feel pressured and uncomfortable. Please stop asking."
I basically said the latter to this person. She laughed, said "hey, there's no harm in asking - I'll keep asking, and you can say no if you want lol" and continued to ask.
I stopped replying and basically avoided her as much as possible.
Good luck dealing with her. I feel for you!